Nemut-tokei (left) & Oki-tokei (right).
Haven't you ever been late for school or work because the alarm clock didn't ring at the time it had been set for?
Or haven't you ever waken up on a holiday morning because the alarm clock ring although you hadn't set it for?
The former is a deed of the monster whose name is Nemut-tokei, and the latter is a deed of the monster whose name is Oki-tokei.
(In Japanese, Tokei means clock, Nemut-tokei signifies 'Stay sleeping', and Oki-tokei signifies 'Stay awake'.)
When Nemut-tokei or Oki-tokei does mischief on you, don't get angry. Stay quiet and think,
'Oh, I'm late! But maybe it's good for me. If I had woken up early and had gone out as usual, I would have got into dangerous situation.'
'Oh, what a nice morning! It's foolish to spend such a wonderful day sleeping.'
Nemut-tokei and Oki-tokei will go away when they know their mischief cannot bother you.